1. Field of the Invention
The invention relates to an apparatus for crushing compressible articles, in particular elongated fiberous articles such as logs.
2. Prior Art
When logs are crushed, their relatively long fibers so obtained can be used in wood products industries, for example in wood pulp and in bonded composite wood panels. Logs that would otherwise be scrapped due to foreign matter embedded therein, for example stones, gravel, etc., can thus be utilized when crushed. Other compressible articles, eg. waste material, can be compacted into billets with uses as land fill, ballast, etc.
It is well known to crush materials using a pair of opposed rollers, or a roller and a flat platten. When final shape of the crushed item is relatively unimportant, such crushing can be appropriate because the crushed item tends to assume a slightly curved shape resulting from the curvature of the crushing roll or rollers. When logs are to be crushed to produce relatively long wood fibers, crushing using one or two rollers breaks the fibers, or at least curves them sufficiently to reduce strength of the wood fibers. This reduction in strength is unacceptable in some applications, particularly for composite bonded wood elements. Furthermore, when items having relatively blunt leading edges are fed into a pair of rollers, opposed cylindrical faces of the rollers form a funnel-shaped "nip" which tends to reject the item being fed into the rollers, unless the rollers are spaced sufficiently widely to accept the item. Commonly, when using rollers, an inwardly directed positive feed force to feed the item forcefully into the nip of the rollers would be needed. A positive feed force usually requires a ram means for feeding material into the rollers but the ram tends to produce a discontinuous feeding process.
Furthermore, the ram is likely to exert a considerable force on the rollers requiring heavy support structure and bearings.